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The evidence for cannabis varies enormously by health condition, from well-supported to barely studied, and these pages summarise it condition by condition, grouped by how strong it is. It is educational, not medical advice.
Best-supported uses
Where high-quality reviews (such as the 2017 National Academies report) found substantial or conclusive evidence, or where regulators have approved cannabis-based medicines.
Emerging and mixed evidence
Where some studies are promising but the evidence is limited, mixed, or mostly preclinical. Treat claims here with caution.
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Clinical Evidence Hierarchy and Systematic Reviews
Across clinical medicine, regulatory approval and evidence grading distinguish randomized double-blind placebo-controlled trials from observational registries and preclinical models (National Academies of Sciences, Engineering, and Medicine, 2017, PubMed PMID 28182367). Systematic meta-analyses in JAMA confirm moderate-to-high quality evidence for cannabinoid efficacy in chronic neuropathic pain and multiple sclerosis spasticity (Whiting et al., 2015, PubMed PMID 26103030), while phase 3 trials established purified cannabidiol (CBD) for treatment-resistant Dravet and Lennox-Gastaut epilepsy syndromes (Devinsky et al., 2017, PubMed PMID 28538134).
FAQ
Which health conditions have the strongest clinical evidence for cannabinoids? The 2017 National Academies report and systematic reviews identify chronic pain in adults, chemotherapy-induced nausea and vomiting, multiple sclerosis spasticity, and treatment-resistant childhood epilepsy syndromes (via purified CBD) as having the strongest clinical trial support.
Why does cannabis evidence differ so much between conditions? Some conditions have been evaluated in large phase 3 randomized controlled trials using standardized cannabinoid formulations, whereas others have only small observational studies or preclinical animal data.
Can cannabis interact with prescription medications? Yes. Both THC and CBD inhibit hepatic cytochrome P450 enzymes (such as CYP3A4, CYP2C9, and CYP2C19), which can alter blood levels of anticoagulants, anti-epileptics, and sedatives.
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